Holographic display technology is considered to be an ultimate solution for realizing 3D display. The backlights of the existing holographic displays use a laser or light emitting diode (Light Emitting Diode, LED) light source plus a beam expanding collimator lens to provide beam expansion and collimation for the light source, so as to illuminate the entire spatial light modulator.
In general, a spatial light modulator contains many individual units spatially arranged in a one-dimensional or two-dimensional array, each of which may be independently controlled under an optical signal or an electrical signal, and change its own optical properties according to such signal, thereby modulating the light wave illuminated thereon. The devices of such category may change the amplitude or intensity, phase, polarization state and wavelength of the light distribution in space, or convert incoherent light into coherent light, under the control of an electrical drive signal or other signals which varies or vary over time. The spatial light modulators can be generally divided into reflective type and transmissive type according to different readout manners of reading-out light; and may also be divided into optical addressing type and electrical addressing type according to different manners of inputting a control signal. The most common spatial light modulator at present is liquid crystal light valve.
In the prior art, since the backlight source needs many optical members to constitute a huge optical system, there is a large overall volume, and displaying can only be provided on one side.